225 
fxus61 kcle 211546 
afdcle 


Area forecast discussion 
National Weather Service Cleveland Ohio 
1046 am EST Sat Nov 21 2009 


Synopsis... 
high pressure will build over the region today and then move to New 
England by the end of the weekend. A weak disturbance will move 
across the area Monday and Monday night. A low pressure from the 
plains will move towards the area for midweek. A cold front is 
expected to cross the region on Wednesday. 


&& 


Near term /until 6 PM this evening/... 
high pressure is over the area and the question is will the clouds 
decrease any and will the sprinkles continue. Some decrease in 
clouds will occur especially over Northwest Ohio. Included that in 
the updated zones/grids. Elsewhere continued with the mostly 
cloudy and the temperatures look OK. Continued the threat of 
sprinkles mainly in the eastern areas this afternoon as per the 
radar upstream and a weak short wave would be moving through. 


&& 


Short term /6 PM this evening through Tuesday night/... 
high pressure continues to hold on across the area tonight and 
Sunday. Models diverge on Monday with GFS a bit stronger with probability of precipitation 
compared with NAM especially across eastern areas. Leaned towards 
lower probability of precipitation then with surface high still off to the northeast 
ridging into the area. This high will help support drier air at 
the lower levels across the area which will inhibit widespread 
showers despite an increase in moisture from a weak disturbance 
that is expected to track northeast through the Ohio Valley and 
into central PA. 


The more significant feature will come towards midweek with low 
pressure approaching from the Midwest. GFS and European model (ecmwf) are still 
considerably different in timing of frontal passage ranging from 
early Wednesday morning to Wednesday night. Canadian closer to GFS 
solution bringing the front through quicker. With continued 
timing discrepancies went with chance probability of precipitation from Tuesday night 
through Wednesday night given lack of confidence to increase them 
at a particular period this far out. 


&& 


Long term /Wednesday through Friday/... 
models continue to advertise a relatively deep but progressive 
trough to swing through. Trough actually is carved out in two 
phases...the first on Wednesday with a second wave later 
Thursday/early Friday. Both the European model (ecmwf) and GFS close off an upper 
low with both systems although the details are not yet clear and 
where and how deep the upper system will ultimately become. The 
GFS is a little faster that the European model (ecmwf). It appears that the coldest 
air will come with the second wave by Thanksgiving night. Models 
show the boundary layer rather warm (+7c) Thanksgiving morning so 
do not want to rush the cold air. Will mention rain mixed with 
snow later in the day. There is bound to be plenty of leftover 
clouds into Friday. Not sure about how organized the lake effect 
will be... with such a strong upper system there is often enough 
directional shear that the lake enhancement dominates. The wind 
becomes west to northwest by Friday but the coldest air aloft is 
starting to lift out. Do feel confident enough to raise the 
probability of precipitation Thursday and Thursday night to 40-60 
percent which is higher than guidance and would not be surprised 
if we have to keep increasing the chance as we get closer. For 
Tuesday and Tuesday night a cold front approaches the area with 
some showers...the front moves through late Tuesday. The GFS 
really cools temperatures off quickly...but for the time being 
just left it as rain as the GFS seems to be the coolest of the 
models. 


&& 


Aviation /16z Saturday through Wednesday/... 
mostly minor aviation issues as a short wave swings across the 
lower Great Lakes this morning. MVFR stratocumulus widespread 
across NE Ohio/northwest PA with a few IFR patches of stratus down wind of 
Lake Erie will persist through middle morning with a few sprinkles. 
Clear patches of sky across Northwest Ohio should fill back in this 
morning. All sites should become VFR this afternoon and skies 
should gradually clear from west to east late afternoon into 
evening. With clear skies and light winds tonight and dewpoints 
relatively high for this time of year there will be fog 
developing. Do not have a good feel on how dense the fog might be 
but IFR visibility possible at most sites. 


Outlook...MVFR developing Tuesday tr Tuesday night. 


&& 


Marine... 
surface high pressure system will pass almost overhead today into 
tonight and the lake will settle down. Winds will veer from a west 
southwest direction to northeast to east by Sunday but the gradient 
will remain light and we should be able to keep the surface winds 
relatively light for several days...rather unusual for middle November. 
That will end by middle week as southeast to south winds will increase 
ahead of the next front by Wednesday with a secondary front pushing 
across the lake by Friday. With plenty of cold advection and a 
decent surface low moving across the northern lakes will forecast 
winds a little higher than guidance by the end of the week. 


&& 


Cle watches/warnings/advisories... 
Ohio...none. 
PA...none. 
Marine...none. 


&& 


$$ 
Synopsis...Abe 
near term...kieltyka 
short term...Abe 
long term...kosarik 
aviation...kosarik 
marine...kosarik